The present invention relates to an automatic sewing machine for joining elements of a workpiece clamped within a work clamp. The automatic sewing machine comprises a reciprocating needle which penetrates the work clamp containing a workpiece consisting of several components. The components of the workpiece are arranged in overlapping relationship, so as to allow for a join and sew operation. The sewing machine also contains a control which effects a relative displacement of support for the work clamp and sewing instrumentalities in such a manner that a joining operation may be executed progressively along the desired path on the workpiece clamped by the work clamp. The work clamp comprises three elements one of which is fixed on the support. The other two elements are movable relative to the fixed element. The arrangement of elements being such that, when the elements are closed, the components of a workpiece are clamped adjacent in such a manner that a join and sew operation can be effected.
U.S. Pat. No. 4,171,672 describes such a machine. In this machine, the work clamp requires the operator to first position the two components of the workpiece relative to each other this positioning usually relies on previously applied stitch markings on at least one of the two components, it presents the thus positioned components to the work clamp, while holding both of them in position one with the other. The handling of the workpieces in this manner is not reliable, however, because the shape of the elements of the work clamp tends to render difficult the presentation of the located components of the workpiece, so that the relative location of the workpieces is uncertain. Furthermore, when the operator relies on stitch markings, the latter are covered by the element located along the marking so that the operator cannot readily verify that the positioning has been maintained and furthermore, when presented to the clamping elements, the latter themselves cover the workpiece component carrying the stitch markings, in the vicinity thereof, so that the operator cannot be sure that the components of the workpiece are properly located with respect to the clamping elements. In the aforementioned document, different types of clamp elements are described and are intended to remedy the disadvantages which arise by the clamping elements obscuring the stitch markings, but, in many cases, the use of the clamping elements of that machine renders the handling of workpieces difficult. Clearly, if the workpiece components are not properly positioned in relation to one another, the finished workpiece may be less than satisfactory.